The present invention relates to an image forming apparatus in an electrophotographic copying machine, laser printer and the like, more particularly to an improved sheet guide device in an image section.
Conventionally, in the transfer section in such apparatus, a transfer charger 92 and a separation charger 93 are disposed opposite to a photosensitive drum 91, and a sheet guide 94 is fixed on the separation charger 93 as illustrated in FIG. 10. A transfer paper 95, which is used for image transfer, entered into the transfer section via register rollers 100 is then conveyed, after passing the chargers 92, 93 and the sheet guide 94, to a fixing section by a conveyor belt 96 and another sheet guide 97. The fixing section receives the transfer sheet 95 into the nip section between a heat roller 98 and a pressurized roller 99 pressed by the heat roller, and fix transferred images on the transfer paper 95.
Accordingly, the transfer paper 95 passed the transfer section reaches the fixing section smoothly passing through an ordinary paper feed path, and the dashes into the nip section between the heat roller 98 and the pressure roller 99. The rear end of transfer paper 95 becomes free right after it passed through a pair of register rollers 100 and passes the transfer section. However, a proper gap is required for the transfer paper 95 sufficiently enough to pass through between the sheet guide 94 and the photosensitive drum 91. When the rear end of transfer paper 95 passes the transfer section after slipping out of the register rollers 100, the rear portion of the transfer paper tends to hang down as shown by a phantom line in FIG. 10, and causes defective transfer as the paper is not held sufficiently thereby parting the photosensitive drum 91.
When the transfer paper dashes into the fixing section, the leading end of the paper first hits the heat roller 98, and the paper is bounced back by .DELTA.S a moment by the shock as shown in FIG. 11, and it affects the rear portion of the paper 95 being transferred with vibration as in FIG. 12.
As the peripheral speed of the heat roller 98 is a little slower than the speed of the transfer paper being conveyed (the peripheral speed of the photosensistive drun 91), there form an arch cuerve at the leading end of the paper 95 as in FIG. 13 and it is transmitted to the transfer paper 95 being transfereed which is in contact with the drum 91 as illustrated in FIG. 14 resulting in some gap between the surface of drum 91 and the paper 95 as well as difference in speed, thereby causing defective transfer and thus spoil the quality of images transferred.